关键词: |
Block copolymers, Transport properties, Nanocomposites, Membranes, Nanoparticles, Conductivity, Computer simulations, Mechanical properties, Ionic liquids, Electrochemistry, Morphology-property correlations, Multiresolution simulation, Polymer-nanoparticle mixtures, Self-assembled morphologies, Il (ionic liquids), Electrochemical properties, Polymerized il |
摘要: |
Major Goals: Electrochemical devices such as batteries and fuel cells have recently become popular in the quest for clean and sustainable energy sources. Electrolytes that facilitate ion transport between electrodes are key components in such devices, and polymeric membrane materials have emerged as attractive candidates for such functions. However, high ionic conductivities in polymeric materials are often obtained in rubbery polymers which lack the requisite mechanical strength for solid state batteries. In an effort to enhance the mechanical properties of such polymer membranes, a variety of strategies have been explored, such as cross-linking of the conductive homopolymers, use of inorganic fillers (to create polymer nanocomposite membranes) and using diblock copolymers in which a mechanically strong block complements the conducting phase. While experiments have successfully demonstrated that the enhancement in the mechanical properties can be achieved without a concomitant deterioration of the conductivity and/or other transport properties, a number of intriguing observations have also been noted in the dependencies of transport properties upon the physicochemical parameters characterizing the polymer membranes: (i) In the context of nanocomposite membranes, the addition of nanoscale particles have in some instances been shown to {\em enhance} the conductivity of the matrix above that of the pristine polymer matrix. Moreover, such enhancements were shown to be highly sensitive to the size, the loading, and the type of the nanofillers. Such observations contradict the conventional wisdom which would suggest that addition of (non-conducting) particles would block the diffusion pathways (by a factor which depends only the loading of the fillers) and lead to reduction in the conductivity of the ions. |